1. Field of the Invention
The present invention relates to a polarization means suitable for observing three-dimensional image information and its position holding mechanism.
2. Description of Related Art
Conventionally, various technological attempts have been made to realize a three-dimensional image display. In many fields of treating images, such as photographs, movies, and television, image display methods relating to three-dimensional images have been studied and put into practical use.
The image display methods relating to the three-dimensional images are classified roughly into a glasses system and a non-glasses system. In either system, images with parallax are separately received by the right and left eyes of a viewer, respectively, so as to be seen as three-dimensional images. Among these, as typical examples of the glasses system, there are a so-called anaglyph system in which a pair of red and blue filtered glasses are worn and a polarized-glasses system.
Color separation systems, such as the anaglyph system, have many disadvantages in quality, such as difficulty of expressing color, degradation of a field of view, etc. Further, the polarized-glasses system suffers from the problem that it is generally necessary to use two projection apparatuses. However, a system allowing a three-dimensional image display with a direct vision type image display device has been proposed in these years.
An outline of a three-dimensional image display apparatus using the polarized-glasses system is shown in FIG. 18.
A three-dimensional image display apparatus 65 has a structure including a liquid crystal panel section 59 and a wavelength division plate filter 64 attached to the liquid crystal panel section 59. In the liquid crystal panel section 59, a pair of transparent support substrates 74a and 74b are provided between a polarizing plate 106, which has a polarization angle illustrated diagonally upward to the left, and a polarizing plate 96, which has a polarization angle illustrated diagonally upward to the right. A liquid crystal image display section 75 having a plurality of sets of pixel parts (red) 78R, pixel parts (green) 78G, and pixel parts (blue) 78B is provided between the pair of transparent support substrates 74a and 74b. 
The wavelength division plate filter 64 is provided in front of the liquid crystal panel section 59. For example, a wavelength division plate (half wave plate) 76 for changing the polarization direction is disposed on one side (back) of a transparent support substrate 74c for every other horizontal line of the pixel sequence of the image display section 75 (note that, although the drawing shows several of them in the interests of brevity, in fact many plates are provided, and the same applies to the following wave length division plate filter 64). The wavelength division plate filter 64 is also referred to as a “micro pole” or a “micro polarizer”.
According to the three-dimensional image display apparatus 65 of a such structure, the direction of a linear polarized light, which is emitted forward in a predetermined direction from the liquid crystal panel section 59, is rotated by 90 degrees due to an action of the wavelength division plate filter 64, so that respective linear polarized lights from odd lines and even lines of a display screen are changed to be in the mutually orthogonal direction.
In other words, for example, as for the odd lines, the linear polarized lights are emitted as they are, without changes, from the liquid crystal panel section 59. On the other hand, as for the even lines, the linear polarized lights directed in the direction orthogonal to the linear polarized lights from the odd lines are generated by the action of the wavelength division plate filter 64.
Each of such polarized lights is observed by means of polarizing plates 69 (for example, a pair of polarized glasses) that are disposed in the proximity of a viewer's eyes. In other words, the polarizing plates 69 have a polarizing plate member 57R which has a polarization angle illustrated diagonally from the lower left to the upper right and a polarizing plate member 57L which has a polarization angle illustrated diagonally from the lower right to the upper left and orthogonal to that of the former, in which the right eye 72R receives a polarized light of an image for the right eye through the polarizing plate member 57R and the left eye 72L receives a polarized light of the image for the left eye through polarizing plate member 57L. By observing both images through the polarizing plates 69 in this way, the viewer can observe a three-dimensional image in full color without flickering.
However, when the wavelength division plate filter 64 is mounted and built into the three-dimensional image display apparatus 65, its installation must be reliably fixed in a position corresponding to a predetermined area (pixel position) of the three-dimensional image display apparatus 65, which is not easy, and the following problems may arise.
In other words, one of the problems is that the image display system is a system in which an image display surface is divided into the predetermined areas, so that it is necessary to render the divided areas of the image display surface as fine as possible, in order to obtain a higher resolution.
Since a finer pixel part for the image display surface has been developed according to a demand for higher image resolution, the liquid crystal panel section 59 of a high definition image display surface having fine division areas is available. However, producing the high definition wavelength division plate filter 64 corresponding to this by means of another separate process and accurately mounting and securing a division pattern of the wavelength division plate filter 64 corresponding to a division pattern (i.e., predetermined pixel parts) of the image display surface are very difficult.
Even if it is possible to mount and fix the wavelength division plate filter 64 accurately, the fixation is generally performed by means of adhesion, such as resin adhesives, for example, so that displacement tends to occur during curing the resin or before it is set, even if it is once adjusted to temporary positioning. Further, it is often the case that displacement of the wavelength division plate filter 64 occurs because of several factors, such as vibration during conveyance and heat.
As to the quality of the material of the wavelength division plate filter 64, it is often the case that a heavy glass substrate is generally used in order to maintain accuracy at the time of being mounted at the predetermined areas, and due to a problem in its production, the glass substrate tends to be displaced because of its own weight. In addition, due to the conditions of durability, such as degradation of a fixing material, the wavelength division plate filter 64 may be displaced. Once displacement of the cured fixing material occurs, it is sometimes very difficult to correct the position, so that it may become impossible to use the costly liquid crystal panel section 59, which is wasteful.
Further, as to the three-dimensional image display apparatus 65, when observing the three-dimensional image, it is necessary to determine the optimal position of the wavelength division plate filter 64 according to conditions such as the positions and height of both eyes of a viewer. There is still another problem that the position of the wavelength division plate filter 64 fixed in advance is not always the optimal position when in observation.
Due to the above factors, if the wavelength division plate filter 64 is displaced with respect to the image display section 75 by several percent to a few tens percent (for example, about a few tens of micrometers), the displacement may partially mix optical information data with one another among the pixel part 78R, 78G and 78B and cause cross talk, thus being amplified and observed.
When the wavelength division plate filter 64 is installed in the correct position, each of the corresponding lights from the respective pixel parts 78R, 78G and 78B always passes through a corresponding wavelength division plates 76 or a corresponding space between the wavelength division plates 76, and the lights do not interfere mutually.
However, when the wavelength division plate filter 64 is fixed in inclined attitudes, if this displacement amount is as small as several percent to a few tens percent with respect to the sizes of the pixel parts 78R, 78G and 78B, or if an absolute value of the displacement is about 50 micrometers, perpendicular displacement amounts at both sides of the liquid crystal panel section 59 are further increased, so that the lights from the respective corresponding pixel parts 78R, 78G and 78B may not pass through only the corresponding wave plate 76 or only the corresponding space between the wave plates.
As a result, the cross talk in an image occurs among the respective pixel parts 78R, 78G and 78B (among the lines, here), thus suffering from the problem that a good three-dimensional image cannot be displayed.
As shown in FIG. 19, a three-dimensional image display apparatus, as in a prior application, includes a notebook computer 60 having attached thereto a liquid crystal panel section 59 that is openable/closable and the wavelength division plate filter 64 that can be attached to the liquid crystal panel section 59, for example.
The notebook computer 60 has the liquid crystal panel section 59 in a liquid crystal image display section 84 which has a foldable structure, so that an image including parallax may be displayed by the liquid crystal panel section 59. The liquid crystal panel section 59 itself may be one that is used for the image display section of a usual notebook computer. For example, when an application for displaying a three-dimensional image is not in operation, it is possible to display the usual images (video image, still image, etc.).
Disposed on the front side facing the liquid crystal panel section 59 is a keyboard section 88 including keys suitable for inputting an alphanumeric character, a hiragana character, a katakana character, etc. and various control keys, etc. Being integral with the keyboard section 88, a palm rest section 87 is provided on a viewer's side. A pointer pad section 86 is provided in the central part of this palm rest section 87.
The keyboard section 88 side is connected to the liquid crystal panel section 59 through a hinge section 66, and the liquid crystal panel section 59 may pivot with respect to the hinge section 66. Therefore, the three-dimensional image viewer can adjust the angle of the liquid crystal panel section 59 by pivoting the hinge section 66 to a desired angle for comfortable viewing.
A position adjustment pattern display program is installed in a hard disk (not shown) of the notebook computer 60. The program is read into a central processing unit of the notebook computer 60 and executed so that a position adjustment pattern is displayed on the liquid crystal panel section 59.
A frame section 85 made of a synthetic resin, for example, is provided around the image display section 84. The computer 60 has a structure in which the liquid crystal panel section 59 is held by the frame section 85 at the image display section 84.
A protruding part 82, which is formed to protrude at a part of the frame section 85, is provided under the image display section 84. The protruding part 82 sufficiently protrudes so as to hold and be in contact with the bottom of the wavelength division plate filter 64. The image display section 84 is formed so as not to suffer from trouble when it is turned and folded up toward the keyboard section 88 side.
As described above, the wavelength division plate filter 64 is a polarization control section in which the wavelength division plates 76 in stripes are disposed every other horizontal line of the respective pixel parts 78R, 78G and 78B.
There is a case, as shown in FIG. 20A, where a spatial relationship between the image display section 75 and the wavelength division plate filter 64 may not be arranged correctly in the three-dimensional image display apparatus 65.
In this case, as for the relationship between the arrangement direction of the respective pixel parts 78R, 78G and 78B of the image display section 75 and the arrangement direction of the wavelength division plate 76, the wavelength division plate filter 64 having a plurality of wavelength division plates 76 may lean slightly, so that the amount dl of the perpendicular displacement may be several percent to a few tens percent of the pixel parts in size. For example, assuming that the pixel parts 78R, 78G and 78B have sizes of 250 micrometers, ⅕ thereof, which is about 50 micrometers, may be displaced.
As a result, some components of the lights from the pixel parts 78R, 78G and 78B may not pass through the corresponding predetermined wavelength division plates 76, so that cross talk may take place among the respective pixel parts 78R, 78G and 78B. It is necessary to inhibit such cross talk from generating in order to display the optimal three-dimensional image, which needs a position adjustment operation.
Thus, as shown in FIG. 21B, the wavelength division plate filter 64 is arranged in the correct position, and each wavelength division plate 76 is provided on a line constituted by the pixel parts 78R, 78G and 78B of the image display section 75 so as to overlap the line exactly, which can be carried out by monitoring a display pattern for position adjustment displayed on the image display section 75 via the polarizing plates 69.
Therefore, the lights from the pixel parts 78R, 78G and 78B can pass through corresponding predetermined portions of the wavelength division plate 76. At the same time, the lights from the pixel parts, except for specific pixel parts, may not pass through the wavelength division plates, so that any cross talk does not occur and a high definition three-dimensional image can be displayed.
Thus, the reliable position adjustment of the transparent support substrate 74c allows a real time position check, and the position adjustment also allows displaying the three-dimensional image without causing a cross talk, whereby the high definition wavelength division plate filter 64 can be used always in the optimal state, it is always possible to observe a three-dimensional image of high definition, and there is a high sensation of reality in the optimal state.
In addition, as for an image display of multi-screens, its resolution may be highly improved, thereby to provide an image display without any cross talk among the respective pixels 78R, 78G and 78B. Further, the position setting of the wavelength division plate filter 64 may be carried out by the viewer himself or herself. Thus, it is possible to understand the principle of the three-dimensional image display so that it may be employed for the education of image engineering. Still further, it provides an advantage that it is possible to save time and efforts for fixing in advance the position of the wavelength division plate filter 64 when shipping.
However, even if the wavelength division plate filter 64 is adjusted in the correct position as described above, there are still problems, as follows,
As shown in FIG. 21, these will be described referring to the figure showing the condition of separation and incidence of lights in the structure of FIG. 18.
First, images 73R for the right eye and images 73L for the left eye are displayed for every other horizontal line on the image display section 75. Further, the polarizing plate 96 is provided on the viewer side of the image display section 75, which has the polarization angle diagonal from the lower left to the upper right illustrated by a virtual line.
Further, on the viewer side of the polarizing plate 96, a wavelength division area 76a which permits the light polarized in the direction diagonally upward to the right to pass therethrough without changing the polarization direction and a wavelength division area 76b which has a half wave plate having a function of polarizing a light by 90 degrees to a polarization direction diagonally upward to the left are provided so as to correspond to respective images on the image display section 75 in which the images 73R for the right eye and the images 73L for the left eye are alternately displayed in ever other horizontal lines.
In this structure, the viewer wears the polarizing plates 69 (for example, a pair of polarized glasses) including the polarizing plate members 57R and 57L having the polarization angle respectively adapted to the images 73R for the right eyes and the images 73L for the left eye which are in horizontal lines and arranged every other line, so that the images 73R for the right eye are received by the viewer's right eye 72R and the images 73L for the left eye are received by the left eye 72L independently so as to view the three-dimensional image.
In other words, the images 73L for the left eye through the wavelength division areas 76b on the even lines, the polarization angles of which are rotated by 90 degrees diagonally upward to the left by means of the half wave plates, can not be observed through the polarizing plate member 57R for the right eye which has the polarization angle diagonally upward to the right. Only the images 73R for the right eye through the wavelength division areas 76a on the odd lines whose polarization angles are in agreement can be observed.
On the other hand, the images 73R for the right eye through the wavelength division areas 76a on the odd lines, the polarization angles of which are orthogonal to the even lines, cannot be observed through the polarizing plates 57L for the left eye having a polarization angle diagonally upward to the left. The images 73L for the left eye through the wavelength division area 76b on the even lines, the polarization angles of which are rotated by means of the half wave plate by 90 degrees diagonally upward to the left, may be observed.
As to the polarizing plate member 57L for the left eye, the images 73R (odd lines) for the right eye, whose entry into the polarizing plate member 57L for the left eye is undesirable, are completely inhibited by the polarization angle of the wavelength division area 76a that permits the lights polarized by means of the polarizing plate 96 having the polarization angle diagonally upward to the right to pass therethrough as they are, which may not cause a problem that they enter the polarizing plate member 57L for the left eye.
However, as to the polarizing plate member 57R for the right eye, since the wavelength division area 76b made of the half wave plate whose polarization angle is rotated diagonally upward to the right has a wavelength dependence characteristic {(each rotation (polarization) angle differs from others depending on each wavelength)}, it is difficult to correctly polarize (rotate) every light in the whole visible light range by 90 degrees. Therefore, the images 73L, for the left eye, whose entry to the polarizing plate member 57R for the right eye is undesirable, cannot be completely inhibited, so that some of the lights may leak and cause a cross talk.
Referring to FIG. 18, when the viewer observes the three-dimensional image with the right eye 72R and the left eye 72L via the polarizing plates 69, the viewer's observing angle and position with respect to the image display section 75 may often differ depending on the situation.
In this case, if the position of the wavelength division plate filter 64 is optimized and fixed by the above mentioned position adjustment mechanism, the angle and position of the polarizing plates 69 (for example, a pair of polarized glasses) change depending on conditions such as the viewer's seated height, so that the distance (space) and the degree of parallelism between the wavelength division plate filter 64 and the polarizing plates 69 may change and, further, a central position misalignment may happen.
Thus, it becomes difficult to hold the optimal distance between the wavelength division plate filter 64 and the polarizing plates 69. If the central positions of the wavelength division plate filter 64 and the polarizing plates 69 are misaligned, the entry amount of the polarization lights incident to each of the polarizing plate member 57R and 57L may decrease, the focuses of the lights incident to the left and right eyes may shift and it becomes difficult to carry out image focusing. In some cases, a cross talk, etc. may arise because of interference among incident lights, so that it becomes difficult to observe the three-dimensional image clearly.
In order to prevent the above described difficulties, the viewer himself/herself must adjust, each time, the polarizing plates 69 to the optimal distance and the optimal position with respect to the wavelength division plate filter 64, which takes time and effort and may cause poor adjustment.
In view of the above, the present invention provides a polarization means and a position holding mechanism with a polarizing plate which allow obtaining an always clear three-dimensional image easily, correctly and quickly.